The Stasis Shot ability gives your assault rifle the power to launch its own version of the Stasis Grenade, freezing opponents on the screen for several seconds within any battles. Stasis effect from about 4.3 seconds to 6.9 (depending on its level).

Adds possibility to activate aggressive battle mode during the battles

15 + 500

Normal Battle Mode: You will automatically hide behind an energy shield during any battle to prevent sudden death and serious injures each time after your target is killed. Shield absorbs about 70% of all types of damage.Attack Battle Mode: Increases damage from 10% to 20% (depending on its level) at the cost of reducing defense (down to 30%). Unlike normal battle mode, you will not auto-crouch between enemy kill and will automatically choose the next target.

I have upgraded psi whenever I can. I am now at psi level 9. At next level it would be more than 4k damage, 1.5k stealing health (only when the enemy is killed). I have battle mode but I almost never use it. Dont have enhanced optics. Later you will need psi to finish off enemies (Chosen One, Xi) who will keep resurrecting unless killed with psi.

battle mode is an interesting thing, some people never use it, while people like me always use it… for mx efficiency, switch on battle mode as soon as battle starts, u get some valuable damage added bonus, the plus is that the cool down finishes just before they start shooting, so u can switch it off again…

optics is imp in the later stages of the game, also it helps if u have recon vulnerability… i had reserched all 4 levels by the end of the game…

ironically, psi is extremely important in the game, until u get acid canon… in some cases it is essential, but in very later stages, u urself will not want to spend crystallite…
in later guns, almost every weapon requires crystal for prod. + upgrade… so u will many a times run out of it… psi should be used mainly for difficult battles where u require health… otherwise for a simple damage,it is not feasible…

According to the info found on this site, thd answer to your questions is:
1. No, it does the the same amount of damage as your equipped shotgun, but this damage acts like a frag grenade. 100% to your target, and splash to its surroundings.
2. The weapon uses 2 shotgun shells. So yes, the grenade stockpile do not matter.

i’m at the point where i had to use shotgun (just unlocked Chopper Shotgun, the weakest shotgun) because my shotgun shells are bursting at 50 !